1. Field of the Invention
The present invention relates to a fabricating method of a liquid crystal display apparatus, in particular, a fabricating method of a liquid crystal display apparatus having a color filter free of blurring of colors at a boundary region of coloring portions, thereby displaying a clear and high quality color image.
2. Description of the Related Art
In a conventional liquid crystal display apparatus, two electrode substrates are faced with a cell gap. Each of the electrode substrates has electrodes that generate pixels. A liquid crystal layer is held between the two electrode substrates so that the peripheral portion of the liquid crystal layer is sealed. In this manner, the principal portions of the liquid crystal display apparatus are constructed.
This construction can be applied for both a simple matrix type liquid-crystal display apparatus and an active matrix type liquid crystal display apparats.
In a liquid crystal display apparatus that can displays an color image on the screen, a color filter is used.
The color filter is constructed by disposing color cells of three primary colors or a plurality of hues such as R. G. and B (red, green, and blue) or Y, M, and C (yellow, magenta, and cyan) corresponding to individual pixels on at least one of the two electrode substrates.
For example, in a color dot matrix liquid crystal display apparatus of the simple matrix driving type, a scanning electrode substrate having scanning electrodes horizontally patterned in a strip shape and a signal electrode substrate having a color filter and signal electrodes vertically patterned in a stripe shape are disposed in face of, with a gap (referred to as a cell gap), in such a manner that the scanning electrodes are disposed nearly perpendicular to the signal electrodes. A liquid crystal material is held in the gap and the peripheral portions of the substrates are sealed.
In a color liquid crystal display apparatus of the active matrix driving type, a TFT array substrate and an opposite substrate are faced with a cell gap. The TFT array substrate has thin film transistors (referred to as TFTs), pixel electrodes, scanning lines, and signal lines. In the TFTs, for example amorphous silicon (referred to as a-Si) is used as a semiconductor layer. A color filter constructed of color cells of for example three primary colors R, G, and B is formed on at least one of the TFT array substrate and the opposite substrate.
The gap is filled with a liquid crystal material and the peripheral portion thereof is sealed. As the liquid crystal layer, nematic liquid crystal with positive or negative permittivity anisotropy is used.
Using the rotating ability of the plane of polarization of light in the nematic liquid crystal, the rotation of the plane of polarization of each pixel is controlled. In addition to the effect of polarization of two polarizing plates that vertically hold the liquid crystal display cells, the transmission of light that passes through the liquid crystal display cells is controlled so as to display an image.
In the liquid crystal display apparatus that displays an image in colors, a color filter is used.
Many fabricating methods of the color filters such as pigment dispersing method, dye dispersing method, electrodepositing method, and printing method. have been proposed. In the pigment dispersing method, a pigment is dispersed to a layer to be colored and thereby a color filter is formed. In the dye dispersing method, a dye is dispersed to a layer to be colored and thereby a color filter is formed. In the electrodepositing method, a color filter is formed by electrodeposition. In the printing method, a coloring material of the color filter that is an ink is printed on a substrate using a printing plate such as an intaglio printing plate or an offset plate. Some of these methods have been practically used.
However, in such conventional fabricating methods, since photo fabricating processes are often used, the process becomes very complicated.
In addition, to deal with pixel sizes that are becoming smaller and smaller, the accuracy of the photo fabrication process should be improved. However, it is difficult to fabricate such color filters with high accuracy and high yield.
In the printing method, although the photolithographic technologies are not directly used, the fabrication of the printing plates is very complicated. Moreover, in the printing method, it is difficult to form precise color filters that correspond to the sizes of fine pixels.
A fabricating method of a fine color filter that does not require the above-described photolithographic process has been proposed. In this method, a coloring material is sprayed onto an accepting layer by an ink jet unit.
However, when a color filter is formed by the ink jet method, the sprayed coloring material may blur with another coloring material at a boundary region thereof. Thus, it is difficult to reproduce clear colors.
Thus, even if color filters with very high throughput are formed by an ink jet unit, the reproducibility of colors of the color filters is low. Consequently, the color reproducibility and display quality of color images of the liquid crystal apparatus using the color filters fabricated by the conventional ink jet method are low.